Light weight, high performance vibration-damping system

ABSTRACT

A light weight, vibration-damping composition having effective amounts of at least one butyl rubber, at least one tackifying resin, at least one pigment and substantially spherical microspheres is disclosed. The present composition has a specific gravity of about 1.0 to 1.2 and has effective damping effects at low temperatures as well as temperatures up to about 60° C. This composition is effective for use in the transportation industry, the building industry, the aerospace industry and the appliance industry.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light weight, high performancevibration-damping system. More specifically, the present inventionrelates to a light weight, elastomeric, butyl, mastic composition whichwhen laminated to a film, provides superior damping properties.

2. Description of Related Art

There is an ever growing need to produce efficient and effectivestructures. This need, coupled with a desire and increasing demand toconserve energy has created light weight structures that move and/orvibrate at faster speeds, producing higher temperatures and thuscreating higher acoustics and undesirably higher levels of vibration.This in turn has necessitated the search for better vibration-dampingmaterials.

It has been known that component parts in devices and structures thatvibrate under the influence of an applied internal or external force canbe substantially reduced by attaching a layer of viscoelastic materialto them. For example, U.S. Pat. No. 3,640,836 discloses avibration-damping laminate in which the viscoelastic layer is a polymercomprised of ethylene, vinyl acetate and acrylic and/or methacrylicacid. U.S. Pat. No. 3,847,726 discloses yet another viscoelasticadhesive composition of a polyepoxide, a polyether amine, a hetrocyclicamine and a phenol useful as vibration-damping material over a -25° C.to +60° C. range. These compositions disclosed, however, are noteffective for vibration-damping over prolonged periods of time and donot provide the required light weight, high performance systems that aredesired in this technological age.

The use of rubbers in a composition for the purpose of vibration-dampingis also known in the art. JP 90-306255 discloses vibration-dampers andsound insulators containing (a) 100 parts composition containing SBR25-40, mineral oil 15-40 and carbon black 30-47%, (b) ≦100 parts(reclaimed) rubbers, (c) 100-600 parts (based on 100 parts a+b)inorganic compounds with specific gravity ≧2.5, and (d) 10-100 parts(based on a+b) fine powdered coal. EP 335642 A2 teaches laminatedcomposites suitable for vibration-damping that are manufactured fromlayers of metal or alloy for support, rubber or a viscoelastic polymerfor damping, and hot-melt adhesive for bonding. The laminate structureis useful for improved sound-proofing applications. JP 61005158 B4discloses sound-insulating and vibration-damping materials havingspecific gravity >2.5 which are prepared by uniting mixtures of 100parts rubber with 150-600 parts non-metallic fibers and/or nonmetallicscaly inorganic substances such as asbestos and mica with metal fibers.These compositions, however, again do not provide the light weight, highperformance, damping effect necessary for the structures in which thepresent invention finds use.

There is therefore, generally, a need for a high performance, lightweight vibration-damping system that allows the industry, especially theautomotive industry, to continue to avail itself of technology thatproduces lighter and lighter cars. Further, there is a need for a highperformance system which will tolerate the temperature ranges of fromabout 0° C. to about 60° C., yet retaining a high sound damping effect.

BRIEF DESCRIPTION OF THE INVENTION

The present invention discloses a unique composition of highperformance, light weight, elastomeric, butyl mastic, that when appliedto a substrate, preferably by lamination, generally provides a superiorvibration-damping system. The composition comprises a mixture of atleast one butyl rubber, at least one tackifying resin, at least onelight weight pigment, and substantially spherical particles. Thespecific gravity of the compositions of the present invention rangesfrom about 1.0 to about 1.20.

More specifically, the present invention comprises a light weightvibration damping system comprising:

(a) a substrate; and

(b) present on at least one surface of said substrate is a light weightvibration damping composition comprising:

(i) about 10 to about 35 wt-% of butyl rubber;

(ii) about 5 to about 20 wt-% of tackifying resin;

(c) about 10 to about 30 wt-% of pigment; and

(d) about 1 to about 10 wt-% of substantially spherical microspheres.

The specific gravity of the compositions of the present invention rangesfrom about 1.00 to about 1.30.

The system may be used in a number of applications, including thetransportation industry, the building industry, the aerospace industryand the appliance industry. The applications in the transportationindustry generally include those parts of the vehicle which are subjectto high vibration levels including the quarter panels, roofs, doors,interior, floor pan and wheel house.

The present invention may also include optional ingredients to furthercustomize the specific properties needed or desired. These can includevarious kinds of fillers and compatible plasticizers such as polybutenesand fatty acids.

Also included within the scope of this invention is the process ofextruding the butyl mastic compositions of the present invention at athickness of about 1.0 to about 3.0 mm onto a release liner and thenlaminating the butyl mastic composition to a suitable substrate, such asaluminum foil, mylar, polyolefin film or steel. This process may also bereversed so that the butyl mastic is extruded unto the substrate andthen laminated with the release liner. The thickness of the substrateshould be about 50 to about 150 microns.

The vibration damping properties are measured by loss factors, andgenerally range from about 0.09 to about 0.60 at temperatures of 20° C.to 60° C. for the systems of the present invention. The systems of thepresent invention also perform favorably at low temperatures as well asat high temperatures. The low temperature performance can be furtherimproved if desired by the presence of a surface seal coating. Thesurface seal coating can be any suitable pressure sensitive adhesivecoating such as described in U.S. Pat. No. 4,581,281 incorporated hereinby reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of the loss factor against temperature for Example 1.

FIG. 2 is a plot of the loss factor against temperature for Example 2.

FIG. 3 is a plot of the loss factor against temperature for Example 3.

FIG. 4 is a plot of the loss factor against temperature for Example 4.

FIG. 5 is a plot of the loss factor against temperature for Examples 2 &4.

FIG. 6 is a description of the damping material used in the dampingperformance in accordance with the described test method.

DETAILED DESCRIPTION OF THE INVENTION

A unique combination of ingredients has been discovered thatadvantageously provides desirable vibration-damping properties. Whenapplied to a suitable substrate such as aluminum foil, Mylar, polyolefinfilm or steel, a light weight vibration damping system is provided. Thesystem can be used in vehicles, such as cars, trucks or boats,appliances or other suitable structures that are subject to noisesresulting from high vibrations.

Generally, the system of the present invention finds application in thequarter panels, the roof, the door, the interior, the floor pan, and thewheel house of motor vehicles. In other applications, the system couldbe placed in a suitable position on the inside or outside of thevehicle, aircraft appliance or structure to provide maximum performance.In use, it has been found that this system has a sound loss factor thatis generally two to three times higher than competitive products whentested under identical conditions as the systems of the presentinvention. Generally, the loss factor values at 30°-40° C. areconsidered the most important for the automotive industry. The lossfactor of prior damping systems are at levels of 0.2 to 0.18. Thedamping effects of these systems drop to negligible levels at highertemperatures. Cured systems, on the other hand, can produce loss factorsup to 0.2 at this temperature range of 30° C. to 40° C., but theirperformance at lower temperatures is poor. The systems of the presentinvention have loss factors ranging from about 0.05 to about 0.7 attemperature ranges of from 20° C. to 60° C., more specifically, lossfactors of about 0.1 to about 0.6 at temperatures of 20° C. to 60° C.,and more specifically, loss factors of about 0.25 to about 0.5 attemperatures of 20° C. to 40° C.. This unprecedented performance caneven be achieved at temperatures as low as 0° C.

Even though prior art systems may have utilized some of the componentsof the present invention in devising their damping systems, the uniquecombinations of the present invention have never been contemplated. Thepresent inventor believes that the tackifying resin plays a key role inthe performance of the system. It is surmised that the tackifying resin,at chosen levels, performs synergistically with the other components ofthe system to increase the loss factors of the systems to unprecedentedlevels.

Generally, the compositions of the present invention comprise at leastone tackifying resin. There are a variety of tackifying resins that areuseful. These include naturally occurring resins and their derivatives,such as aliphatic hydrocarbon resins, rosin and rosin esters, terpene,and coumarone and coumarone-indene. Further, there are syntheticpetroleum based resins which can be used either alone or in combinationwith the naturally derived resins. Tackifying resins are, as their nameconnotes, generally used to provide tack to compositions. However, inthe present invention, they improve the damping effects of the system aswell. The preferred tackifying resins of the present invention includethose known under the trade designation of "Escorez 1102, 1104, 1310 LC,1580, 2000 series and 5000 series" from Exxon Chemical (Houston, Tex.)and "Norsolene" from Sartomer Co. (West Chester, Pa.). In the preferredcomposition, amounts of resins can vary from about 5 to about 20 wt-%with a more preferred amount of from about 5 to about 20 wt-% to a mostpreferred amount of from about 5 to about 17 wt-%. The vibration dampingeffect, as measured by the loss factor, increases as the level oftackifying resin increases. However, at levels higher than about 20wt-%, the system becomes brittle at the low temperature ranges, and thusloses the vibration damping effect. Some of the loss due to brittlenesscan be compensated by a surface coating. The coating can be any surfaceseal coating including any suitable pressure sensitive adhesive coatingsuch as described in U.S. Pat. No. 4,581,281 incorporated herein byreference.

The butyl rubbers that are useful in the present invention may differ ingrades. These butyl grades differ in moles % unsaturation, molecularweight, and nature of the stabilizer incorporated during manufacture toprevent degradation. These include partially crosslinked butyl rubber,copolymers of isobutylene and isoprene. Examples of butyl rubbers of thepresent invention include, but are not limited to, those known under thetrade designation of "Butyl 065, 165, 268 & 269" from Exxon Chemical(Houston, Tex.), and "Kalar 5215", (Belleville, N.J.). In a preferredcomposition of the present invention, butyl rubber is present in anamount of about 10 to about 30 wt-%, more preferably in an amount ofabout 10 to about 25 wt-%, with the most preferred amount of about 15 toabout 25 wt-% of the total system.

Substantially spherical microspheres or fine particles are useful in thepresent invention because of their light weight. They may be useful inproviding bulk, controlling viscosity, increasing cohesive strength andso forth. There are various kinds of spheres or microspheres that couldfind use in the present invention. They include, hollow, substantiallyspherical, or fine particles of ceramic, polymeric and glass or mixturesthereof. The preferred amounts of microspheres in the present inventionare present in an amount of about 1 to about 15 wt-%, more preferably inan amount of about 1 to about 10 wt-%, and most preferably in an amountof about 3 to about 10 wt-%. Examples of suitable fillers include thoseknown under the trade designation "Extendosphere SF" and "Q-CEL" fromThe PQ Corporation (Valley Forge, Pa.), "Fillite 150 & 100" from Fillite(Atlanta, Ga.), and "Scotchlite Glass Bubbles K Series" from 3M (St.Paul, Minn.).

A pigment or combination of pigments can also be used in thecompositions of the present invention to provide color. Among otherproperties, pigments can also be used to increase the solids content ofthe compositions and perform the function of a filler. Generally, anyalkali stable inorganic or organic pigment can be used in thecompositions of the present invention. Examples of useful pigments inthe present invention include carbon black and Austin Black™. AustinBlack™ is a light weight filler containing 77% carbon. The amount ofpigment used in the present invention may vary over a wide range.Preferably, it is present in an amount of about 10 to about 35 wt-%,more preferably in an amount of about 10 to about 30 wt-% and mostpreferably in an amount of about 15 to about 25 wt-%. Suitable pigmentsare known under the trade designations of "Special Black™ 100" fromDegaussa AG (Frankfurt, Germany), "Austin Black™ 325" from Coal Fillers,Inc. (Bluefield, Va.) and "Regal Black™ 300" from Cabot Corp. (Boston,Mass.).

Optional ingredients can also be added to the compositions of thepresent invention for further customization of the system. Theseingredients will generally be used in amounts that do not adverselyalter the desirable properties of the system. Ingredients that may beadded include fillers and plasticizers. Although the ingredients used inthe present invention may be characterized as useful for specificfunctions, it should be understood that these ingredients are notlimited to their typical functions and thus will be used generally inthe present invention to provide desirable properties to the system. Forexample, pigments may also be useful as fillers and so forth.

In order to obtain certain properties such as crack resistance, waterresistance and carbon dioxide barrier effects, platy fillers such asvarious types of mica which includes mica fractionated mallusk shell andphlogopite mica, talc and clay may be used. Further, it may beadvantageous to mix fillers. The preferred amount of filler used in thepresent invention is from about 15 to about 45 wt-%, with the morepreferred amount of from about 20 to about 40 wt-% and most preferablyin an amount of from about 25 to about 35 wt-% of the total system.Fillers are available as naturally occurring or as the result of severalsilicates of varying chemical compositions and are known under thefollowing trade designations, "ROY-CAL-L" from Oyster Shell Products(Mobile, Ala.) "RC-32 clay" from Thiele Kaolin Company (Sandersville,Ga.). "4-K Mica" from KMG Minerals (Kings Mountain, N.C.) and "5000Series Mica" from Polar Minerals, (Mt. Vernon, Ind.).

Plasticizers are generally used with other resins to obtain tack andcohesive strength. A number of plasticizers can be used in the presentinvention in order to obtain these desirable properties. Examples oftypical plasticizers include polybutene, paraffin oils, tall oil fattyacid, petrolatum and certain phthalates with long aliphatic side chainssuch as ditridecyl phthalate. Certain plasticizers under the tradedesignations such as "Parapol 700" and "Parapol 1300" from ExxonChemicals (Houston, Tex.), "Indopol H-50" and "Indopol H-300" availablefrom Amoco Chemicals (Chicago, Ill.) and "Acintol" from Arizona Chemical(Panama City, Fla.) can be used in the present invention. Preferredamounts of the plasticizer of the present invention are available in anamount of about 10 to about 30 wt-% of the total system, with morepreferred and most preferred amounts of about 10 to about 25 wt-% andabout 15 to about 25 wt-% respectively of the total system.

The compositions of the present invention can be mixed in aBaker-Perkins sigma blade mixer and extruded onto a release paper andthen laminated on a suitable substrate such as foil. The process canalso be reversed, i.e., the butyl mastic can be extruded onto thesubstrate and then the release paper is applied.

The vibration damping properties are generally measured using theEngineering Society for Advancing Mobility Land Sea Air and Space, SAEJ1637 test. The test measures the vibration damping performance of asystem consisting of a damping material bonded to a vibratingcantilevered steel bar generally known as the Oberst Bar. The testindicates the loss factors at the temperatures the material is subjectedto. This test procedure is based on the method described in ASTM E 756and differs only in that the SAE practice specifies the bar material,the bar size and the mounting conditions of the test sample.

The loss factors of systems of the present invention, as mentionedbefore, can range from about 0.05 to about 0.70 at temperature ranges of0° C. to 60° C., more specifically from about 0.10 to about 0.60 attemperature ranges of 20° C. to 60° C.

The following non-limiting examples are set forth to illustrate thepresent invention.

EXAMPLES

Test Method

1. Vibration damping based on the Engineering Society for AdvancingMobility Land Sea Air and Space, SAE J1637 test.

This method used a steel bar as the test bar. Precision Ground GageStock (or also called Precision Ground Flat Stock) bars were used as theOberst bar. This Oberst bar could be bought commercially or machinedfrom a mild steel bar stock. When the bar was machined, care was takento ensure that the two faces of the bar were parallel to each other andthat the edges and the ends were square with the face of the bar. A newbar was used for each application. The samples tested had a thickness of2 mm of vibration damping composition on a 100 micron substrate. Thedimensions of the bars varied.

Manufacturing Procedure for Example 3

A Baker Perkins mixer was used. Kalar 5215 (182 kg), Butyl 268 (34 kg),Escorez 1102 (136 kg) and 15 kg of polybutene H50 were added to themixer and mixed for 30 minutes with the cooling water turned on in theJacket. Next, Austin Black 325 (228) was added in increments of 45 kgfor the next 30 minutes. Then FA-2 oil (3 kg) was added and followed by4 K mica (91 kg), RC-32 Clay (114 kg), Roy Cal L (45 kg) and Polybutene(234) kg) in increments while maintaining high shear action (ormasticating action). The entire mixture was mixed until the homogeneousmastic was achieved. Microspheres (45 kg) was added next and was mixedfor 15 minutes. Through the entire process, temperature was maintainedbelow 250° F. Total mix time was 3-4 hours. Quality control test wasmade using needle penetration hardness test and then talc (23 kg) wasadded to the mixer to break up the butyl mastic into smaller chunks sothat it could be easily removed from the mixer. A similar procedure wasfollowed for other examples.

    ______________________________________                                                 Example 1                                                                            Example 2 Example 3                                                                              Example 4                                  ______________________________________                                        Butyl 268  1.5                3.10                                            Kalar 5215 17.38    21.70     16.48  19.39                                    Polybutene H50                                                                           8.36     18.32     20.39  16.36                                    Austin Black 325                                                                         20.9     21.90     20.6   21.35                                    Escorex 1102                                                                             14.00    7.97      12.36  16.0                                     RC 32 Clay 8.36     9.97      10.30  8.90                                     Roy-cal-L  8.36     1.99      4.12   1.78                                     4K Mica    8.36     7.96      8.24   8.90                                     FA-2 Oil   .25      .24       .29    .21                                      Indopol H-300                                                                            8.36                                                               Talc       4.18     1.99                                                      Fillite 150         7.96      4.12   7.10                                     ______________________________________                                    

The samples were tested for damping performance according to the testmethod described Supra. The dimensions of the bars used were as follows:

    ______________________________________                                        Examples           Dimensions                                                 ______________________________________                                        Mounted Free Length                                                                              200 mm ± 0.5 mm                                         Total Length       225 mm                                                     Thickness          0.8 mm ± 0.03 mm;                                       Width              12.7 mm ± 0.03 mm.                                      ______________________________________                                    

SAE J1637 test results are shown in the following table:

    __________________________________________________________________________    COMPOSITE LOSS FACTOR VS TEMPERATURE @ 200 HZ                                 TEMP C.   0  10 15 20 30 40 45 50 60 Sp. Gr.                                  __________________________________________________________________________    Example 1 0.192                                                                            -- 0.374                                                                            0.647                                                                            0.520                                                                            -- 0.250                                                                            -- 0.114                                                                            1.30                                     (FIG. 1)                                                                      172-116 (butyl-2.0                                                            mm Al.-100                                                                    micron)                                                                       1A - 172-116                                                                            0.101                                                                            -- 0.283                                                                            0.451                                                                            0.477                                                                            -- 0.215                                                                            -- 0.097                                                                            l.26                                     (butyl-1.5 mm Al. -                                                           75 micron)                                                                    Example 2 0.230                                                                            0.330                                                                            -- 0.570                                                                            0.510                                                                            0.255                                                                            -- 0.155                                                                            0.100                                                                            1.22                                     (FIG. 2)                                                                      172-165 (butyl-2.00                                                           mm Al.-100                                                                    micron)                                                                       Example 3 0.130                                                                            -- 0.263                                                                            0.427                                                                            0.404                                                                            -- 0.227                                                                            -- 0.093                                                                            1.28                                     (FIG. 3)                                                                      (butyl-2.00 mm Al.-                                                           100 microns)                                                                  Example 4 0.105                                                                            0.211                                                                            -- 0.355                                                                            0.510                                                                            0.660                                                                            -- 0.260                                                                            0.l68                                                                            1.25                                     (FIG. 4)                                                                      172-199' (butyl-                                                              2.00 mm Al.-100                                                               micron)                                                                       4A - 172-199                                                                            0.148                                                                            -- 0.383                                                                            -- 0.331                                                                            -- 0.139                                                                            -- 0.070                                                                            1.28                                     (butyl-1.7 mm Al.-                                                            100 micron)                                                                   4B - 172-199                                                                            0.159                                                                            -- 0.393                                                                            -- 0.372                                                                            -- 0.159                                                                            -- 0.082                                                                            1.25                                     (butyl-2.00 mm Al.                                                            75 micron)                                                                    __________________________________________________________________________     N0TE:                                                                         1A is the same composition as Example 1. 4A and 4B are the same               composition as Example 4.                                                

I claim:
 1. A light, uncured, elastomeric, vibration damping compositioncomprising:(a) at least one butyl rubber; (b) at least one tackifyingresin present in an amount effective for improving the vibration dampingeffect of the composition; at least one black pigment being present inan amount effective for providing and increasing the solids content ofthe composition, wherein the pigment is a lightweight filler having aspecific gravity of less than or equal to 1.31; (d) substantiallyspherical microspheres being present in an amount effective forcontrolling the viscosity and increasing the cohesive strength of thecomposition; wherein said composition is uncured and having a specificgravity of about 1.00 to about 1.20.
 2. The vibration-dampingcomposition of claim 1 wherein the tackifying resin is present in anamount of from about 5 to about 20 wt-% of the total composition.
 3. Thevibration-damping composition of claim 1 wherein the tackifying resin isan aliphatic hydrocarbon resin.
 4. The vibration-damping composition ofclaim 1 wherein the butyl rubber is present in an amount of about 10 toabout 30 wt-% of the total composition.
 5. The vibration-dampingcomposition of claim 1 wherein the pigment is present in an amount ofabout 10 to about 35 wt-% of the total composition.
 6. Thevibration-damping composition of claim 1 wherein the substantiallyspherical microspheres are selected from the group consisting ofspherical micro-balloons and particles of ceramic, polymeric and glass,and mixtures thereof.
 7. The vibration-damping composition of claim 6wherein the substantially spherical microspheres are present in anamount of about 1 to about 15 wt-% of the total composition.
 8. Thevibration-damping composition of claim 1 further comprising aningredient selected from a group consisting of fillers, plasticizers andmixtures thereof.
 9. A vibration-damping composition of claim 1 whereinthe fillers are selected from the group consisting of mica, clay,pulverized mollusk shell and mixtures thereof.
 10. The vibration-dampingcomposition of claim 1 wherein the plasticizer is selected from thegroup consisting of polybutene, fatty acids and mixtures thereof. 11.The vibration-damping composition of claim 1 wherein the butyl rubber isselected from the group consisting of different grades of butyl rubber,partially crosslinked butyl rubber, and copolymers of isobutylene andisoprene.
 12. The vibration damping composition of claim 1, capable ofbeing applied to a substrate selected from the group consisting ofaluminum foil, mylar, polyolefin film and steel.